1. Field of the Invention:
The present invention relates to a method for manufacturing a solid electrolyte capacitor in a chip structure, whereby a sintered member composed of a valve metal (electrochemical vent or valve metal) is built into a system carrier having a cathode terminal and an anode terminal.
2. Description of the Prior Art
Such a method is disclosed, in general, in U.S. Pat. No. 4,483,062, fully incorporated herein by this reference. The system carrier employed therein has separate cathode and anode terminals.
In the manufacture of solid electrolyte capacitors in a chip structure, the integration of the capacitor element (completely coated anode) requires a carefully-matched assembly technology due to the smallness of the dimensions and the sensitivity of the capacitor element. Avoiding mechanical stresses is thereby a special problem. Such mechanical stress conditions can build up when welding and soldering the bridge-like structure between the anode terminal and the cathode terminal and the capacitor element. The junction between the sintered member and the anode wire is thereby the weakest point and, therefore, is particularly jeopardized. It is composed of the metallic contact produced by sintering between individual power drains composed of a valve metal (preferably tantalum) and the anode wire composed of the same material as the sintered member.
Both tensile forces and pressure forces, as well as rotational forces, can occur at this sensitive contact location between the sintered member and the wire. An increased residual current up to a short circuit of the capacitor is the consequence of such mechanical distortions. An increase in residual current can already be experimentally documented on the basis of an elastic distortion. This effect is reversible, i.e. the residual current returns to its original value after the stress is removed.